The present invention relates in general to an airfoil lance apparatus for homogeneous humidification and/ or sorbent dispersion in a gas stream A removable airfoil lance assembly of the invention contains a plurality of atomizers and related supply piping and hardware for in-duct installation in a gas stream. Atomizer shields are provided around the atomizers for the uniform distribution of a shield gas to each atomizer.
There are many reasons for conditioning a process gas stream. These include:
improving particulate collection capabilities (i.e., electrostatic precipitator performance enhancement);
quenching or cooling of a gas stream to meet process requirements or to accommodate process equipment limitations (i.e., gas volume reduction); and
facilitating process chemical reactions where a gas/liquid/solid phase interaction is required (e.g., sorbent injection for sulfur dioxide capture).
It is known to use sulfur trioxide injection into a particulate laden flue gas steam to reduce the resistivity of fly ash particulate. This results in an electrostatic precipitator collection efficiency improvement. Sulfur trioxide injection is typically carried out by conversion of liquid sulfur dioxide or elemental sulfur to sulfur trioxide prior to injection upstream of the electrostatic precipitator
Quenching or cooling of a process gas stream (e.g., flue gas) via humidification is also known and is carried out by spraying a fine rest of water droplets into a process gas stream, giving rise to evaporation of the water droplets and an increase in moisture content of the gas. Humidification to high (80.degree. F. to 100.degree. F.) approaches to saturation temperature (i.e., low to moderate increases in gas humidity) can be easily achieved via installation of a simple spray nozzle in the gas duct. This is particularly true for a particulate free process gas. A typical problem arising in a particulate laden process gas application is the buildup of solids on the spray nozzle. If the deposit grows large enough, it can interfere with atomization spray quality, resulting in large droplets and greater evaporation time requirements. However, at a high approach to saturation temperature, the large temperature driving force for evaporation compensates, to a point, for poor droplet size distribution. Hence, quenching or cooling to high approaches to saturation temperature by means of spray evaporation is carried out frequently in many applications that require an immediate reduction in process gas temperature.
Dry scrubbing technology which depends on the presence of moisture to achieve reaction of sulfur dioxide with sorbent is commercially available for sulfur dioxide removal from flue gases Babcock & Wilcox, Flakt, Joy Niro and Research Cottrell are the major manufacturers of dry scrubbers.
Treatment of flue gas with moisture and with sorbents injected dry or as slurries via the Linear VGA Nozzle is also known (U.S. Pat. No. 4,314,670 to Walsh Jr.).
U.S. Pat. No. 4,314,670 to Walsh, Jr. discloses a linear variable gas atomizing nozzle best illustrated in FIGS. 12 and 13 of that reference. This reference does not offer a low gas stream side pressure drop housing which solves the problem of opposition on the nozzle, however.
An article by William A. Walsh, Jr. "A General Disclosure of Major Improvements In the Design of Liquid-Spray Gas Treating Processes Through Commercial Development of Linear VGA Nozzle,", distributed by the author to solicit interest in this technology, describes improvements in a liquid-spray flue gas treating process which utilizes the Linear VGA Nozzle design. FIG. 3 of this article discloses the nozzle. This reference lacks both an airfoil geometry and shield air provision, resulting in increased process gas side pressure losses and deposition of solids on the nozzle, respectively.
An airfoil lance assembly is discussed in very general terms on page 11 in a technical paper presented to the Energy Technology Conference & Exposition in Washington, D.C. on Feb. 18, 1988. This technical paper mentions a shield air system. There are no drawings depicted in the article, or any details concerning the structure of the air foil lance apparatus.
A technical article by P.S. Nolan and R.V. Hendricks, "EPA's LIMB Development and Demonstration Program," Journal of the Air Pollution Control Association, Vol. 36, No. 4, April, 1986 describes features of a limestone injection multistage burner (LIMB) system at Ohio Edison's Edgewater Station. The arrangement of injectors for sorbent injection is discussed on pages 435-436.
A technical presentation by G.T. Amrhein and P.V. Smith, "In-Duct Humidification System Development for the LIMB Demonstration Project," presented at the 81st Annual Meeting of the Air Pollution Control Association Dallas Texas, June 20-24, 1988, describes the development of an in-duct humidifier with optimum arrangement of atomizers.
A technical presentation by P.S. Nolan and R.V. Hendricks, "Initial Test Results of the Limestone Injection Multistage Burner (LIMB) Demonstration Project" presented at the 81st Annual Meeting of the Air Pollution Control Association, Dallas Texas, June 20-24, 1988, describes the Edgewater LIMB design and operating conditions with the concept of humidification.
Additional references which are relevant to the present invention are U.S. Pat. Nos.:
4,285,838 to Ishida, et al.;
4,019,896 to Appleby;
4,180,455 to Taciuk;
4,455,281 to Ishida, et al.; and
4,285,773 to Taciuk.
None of the above disclosures reveals details or design configurations of an airfoil lance of the present invention, which solves the problems of nozzle deposition and pressure drop.